Reoccuring problem, someone experienced required..

Okay, so unsure where to start here.
Basically after having virtually no problems with gaming online one series seems to be eluding my internet capabilities (which aren't very good) : Call of Duty.

After buying MW2 upon release whenever it was released on my PS3 I immediately was confronted with 'Servers are unavailable, please try again later or visit the Call of Duty website'
Even weeks after release, the problem persisted. I had an xbox around this time and the game worked perfectly on that format.
Long story short; Black Ops, MW3 and now Black Ops 2 all have the same problem.
(Only now the servers are smaller so MW2 and Black Ops 1 both work online now, MW3 and BO2 do not.)

Everytime I attempt to play MW3 or BO2 I am confronted with the same, 'Cannot connect to server' etc.
I am told there are solutions to my problems by various methods, forwarding ports, opening NAT, etc.
But truth be told, I know nothing of these methods because I'm the furthest from technical you could imagine.
I just rang my provider (Orange) and the call centre wasn't my country so I couldn't understand, and I could not be understood, the gentleman said a little about ports, then kind of lost confidence in what he was saying and abruptly hung up.

I really need to get this sorted as now I have more free time I'm becoming a more serious gamer, I have not just paid £40 to play a campaign, after all.

I am with orange on a Netgear N150 wireless modem, router DGN1000
I've currently entered my I.P thing into the address bar to get onto the connection settings and right now I REALLY would appreciate someone to hold my hand and help me through the rest of this!

PS: My signal is as weak as cats P*** so I currently have an Ethernet cable running from the router upstairs and directly into my PS3, from which I am recieving a Type 2 NAT connection.

tl;dr: ports need opening, need better NAT, to help COD work? or maybe theres something else I can do, any help will be appreciated.